1. Field of the Invention
This invention relates to a spinneret having a non-circular cross-section capillary orifice and process for using this spinneret in the production of polyamide yarns having a circular cross-section. In particular, the invention relates to a spinneret for extruding polyamide filaments and forming yarns comprised of the same filaments.
2. Description of the Related Art
In the manufacture of polyamide multifilament yarns, especially nylon 66 yarns, the winding of the yarn must be stopped frequently to remove undesirable deposits found around the capillary exit side of the spinneret plate. If not removed these deposits build up to a thickness of a “few millimeters (per) week” according to Fourne (Synthetic Fibers, Chapter 4, page 359, C. Hanser Publishers, Munich 1998.) Such deposits contributed to the filament bending or “kneeing.” The bending of a majority of the filaments, if not remedied, ultimately led to filaments breaks, yarn defects or unscheduled process interruptions and poor efficiency.
A remedy practiced in the art for filament bending or kneeing is to clean these deposits off the extrusion or spinneret plate on the capillary exit face. This cleaning process is also known as “spinneret wiping.” The cycle time between spinneret wiping events, where each event is necessitated by a build up of the undesirable deposits, is the spinneret wipe life. It is desirable from a process efficiency and continuity standpoint to have a longer spinneret wiping cycle or wipe life.
In general, the cross sectional shape of a filament is determined by the cross sectional profiled shape of the extrusion orifice. For example, in U.S. Pat. No. 5,432,002 a trilobate profile filament yarn is produced by means of a spinneret plate with multiple orifices of trilobate shape. Whereas, a circular profile filament yarn is produced by a spinneret plate, illustrated at 170 in FIGS. 1a and 1b with multiple orifices 100 of circular shape.